# Button head socket cap screw, inch (ASME B18.3)

Button head socket cap screw, Unified inch threads (UNC and UNF) #0-80 to 1/2-20, at any length. Presets cover the
catalogue sizes.

## Geometry

Envelope for assemblies:

- domed head of diameter **A max** and height **H max**, drawn as a spherical cap through the head's rim and top;
- hexagon socket, nominal key size **J**, depth **T** (key engagement, min) measured from the top of the head;
- plain shank at the basic major diameter **D**, length **L** (`length`, under the head); the thread is not modelled.

The head's bearing face is on the XY plane at the origin, the head above it, the shank along -Z.

## Parameters

| Parameter | Meaning |
|---|---|
| `size` | Thread, #0-80 to 1/2-20 (UNC and UNF; no 7/16, see Sources) |
| `length` | Nominal length L under the head, inches |
| `material` | `steel` (alloy steel, black oxide), `stainless-18-8` (304), `stainless-316` |

## Sources

- **D**, basic major diameter (ASME B1.1): NBS Handbook H28 (1969) Part I, Table 2.7 "Unified standard screw thread
  series", column "Nominal size and basic major diameter" (printed p. 2.08,
  <https://nvlpubs.nist.gov/nistpubs/Legacy/hb/nbshandbook28-1969p1.pdf>); the same basic diameters head the B18.3
  tables below.
- **A max, H max, J, T min**: ASME B18.3-2012, Table 11 (hexagon socket button head cap screws), as reproduced at
  <https://www.globalfastener.com/standards/detail_20308.html>; the same values in ASME B18.3-2003 Table 3
  (<https://www.fasten.it/en/norms/norm/asme_b18.3_table_3>, whose H column for #0 and #1 shows the minimum), in
  Holo-Krome's *Technical Manual* (2015) Table 10, p. 12 (<https://holo-krome.com/uploads/7/2/7/5/72754089/hk_consolidated_tech_manual_full_2015.pdf>) and in Unbrako's *Engineering Guide*, p. 15
  (<https://wp.optics.arizona.edu/optomech/wp-content/uploads/sites/53/2016/08/UnBrako-fasteners.pdf>).

The values are the same in the 2003 and 2012 editions; the recipe cites ASME B18.3-2012. The 2012 edition adds a
7/16 size that the 2003 edition and the maker catalogues above don't have; it is not offered here. Inch values as in the standard; the model converts them to millimetres (1 in = 25.4 mm).

| Size | D | A | H | J | T |
|---|---|---|---|---|---|
| #0 | 0.06 | 0.114 | 0.032 | 0.035 | 0.02 |
| #1 | 0.073 | 0.139 | 0.039 | 0.05 | 0.028 |
| #2 | 0.086 | 0.164 | 0.046 | 0.05 | 0.028 |
| #3 | 0.099 | 0.188 | 0.052 | 0.0625 | 0.035 |
| #4 | 0.112 | 0.213 | 0.059 | 0.0625 | 0.035 |
| #5 | 0.125 | 0.238 | 0.066 | 0.078125 | 0.044 |
| #6 | 0.138 | 0.262 | 0.073 | 0.078125 | 0.044 |
| #8 | 0.164 | 0.312 | 0.087 | 0.09375 | 0.052 |
| #10 | 0.19 | 0.361 | 0.101 | 0.125 | 0.07 |
| 1/4 | 0.25 | 0.437 | 0.132 | 0.15625 | 0.087 |
| 5/16 | 0.3125 | 0.547 | 0.166 | 0.1875 | 0.105 |
| 3/8 | 0.375 | 0.656 | 0.199 | 0.21875 | 0.122 |
| 1/2 | 0.5 | 0.875 | 0.265 | 0.3125 | 0.175 |

Preset list: sizes and lengths of the step.parts catalogue (MIT), see `library/NOTICE.md`.